CVE-2026-100779
published 2026-09-29CVE-2026-100779: Use-after-free in the XSLT component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 140.17, Thunderbird 153.4, Firefox 157…
PriorityP347high8.8CVSS 3.1
AVNACLPRNUIRSUCHIHAH
EPSS
0.32%
23.3th percentile
Use-after-free in the XSLT component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 140.17, Thunderbird 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17.
Affected
18 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| mozilla | firefox | < Firefox 157 | Firefox 157 |
| mozilla | firefox | < 157.0.0 | 157.0.0 |
| mozilla | firefox | — | — |
| mozilla | firefox | >= 115.1.0 < 115.42.0 | 115.42.0 |
| mozilla | firefox | >= 140.0 < 140.17.0 | 140.17.0 |
| mozilla | firefox | >= 153.0 < 153.4.0 | 153.4.0 |
| mozilla | firefox_esr | < Firefox ESR 153.4 | Firefox ESR 153.4 |
| mozilla | firefox_esr | < Firefox ESR 115.42 | Firefox ESR 115.42 |
| mozilla | firefox_esr | < Firefox ESR 140.17 | Firefox ESR 140.17 |
| mozilla | thunderbird | < Thunderbird 157 | Thunderbird 157 |
| mozilla | thunderbird | < Thunderbird 153.4 | Thunderbird 153.4 |
| mozilla | thunderbird | < Thunderbird 140.17 | Thunderbird 140.17 |
| mozilla | thunderbird | < 157.0 | 157.0 |
| mozilla | thunderbird | — | — |
| mozilla | thunderbird | >= 140.0 < 140.17.0 | 140.17.0 |
| mozilla | thunderbird | >= 153.0 < 153.4.0 | 153.4.0 |
| rhel10 | firefox-flatpak | — | — |
| rhel10 | thunderbird-flatpak | — | — |
CVSS provenance
nvdv3.18.8HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
vendor_redhat8.8HIGH
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Red Hat
firefox: thunderbird: Use-after-free in the XSLT component
vendor_redhat·2026-09-29·CVSS 8.8
CVE-2026-100779 [HIGH] CWE-416 firefox: thunderbird: Use-after-free in the XSLT component
firefox: thunderbird: Use-after-free in the XSLT component
Use-after-free in the XSLT component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 140.17, Thunderbird 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17.
A flaw was found in Firefox and Thunderbird. The Mozilla Foundation's Security Advisory describes the following issue:
Use-after-free in the XSLT component
Statement: Red Hat Product Security rates the severity of this flaw as determined by the Mozilla Foundation Security Advisory.
Mitigation: Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Pack
Mozilla
Mozilla Foundation Security Advisory 2026-101: CVE-2026-100779
vendor_mozilla·CVSS 8.8
CVE-2026-100779 [HIGH] Mozilla Foundation Security Advisory 2026-101: CVE-2026-100779
Mozilla Foundation Security Advisory 2026-101
CVE: CVE-2026-100779
Product: Thunderbird
Impact: low
Fixed in: Thunderbird 157
Mozilla
Mozilla Foundation Security Advisory 2026-103: CVE-2026-100779
vendor_mozilla·CVSS 8.8
CVE-2026-100779 [HIGH] Mozilla Foundation Security Advisory 2026-103: CVE-2026-100779
Mozilla Foundation Security Advisory 2026-103
CVE: CVE-2026-100779
Product: Thunderbird
Impact: low
Fixed in: Thunderbird 153.4
Mozilla
Mozilla Foundation Security Advisory 2026-97: CVE-2026-100779
vendor_mozilla·CVSS 8.8
CVE-2026-100779 [HIGH] Mozilla Foundation Security Advisory 2026-97: CVE-2026-100779
Mozilla Foundation Security Advisory 2026-97
CVE: CVE-2026-100779
Product: Firefox
Impact: low
Fixed in: Firefox 157
Mozilla
Mozilla Foundation Security Advisory 2026-100: CVE-2026-100779
vendor_mozilla·CVSS 8.8
CVE-2026-100779 [HIGH] Mozilla Foundation Security Advisory 2026-100: CVE-2026-100779
Mozilla Foundation Security Advisory 2026-100
CVE: CVE-2026-100779
Product: Firefox ESR
Impact: low
Fixed in: Firefox ESR 153.4
Mozilla
Mozilla Foundation Security Advisory 2026-98: CVE-2026-100779
vendor_mozilla·CVSS 8.8
CVE-2026-100779 [HIGH] Mozilla Foundation Security Advisory 2026-98: CVE-2026-100779
Mozilla Foundation Security Advisory 2026-98
CVE: CVE-2026-100779
Product: Firefox ESR
Impact: moderate
Fixed in: Firefox ESR 115.42
Mozilla
Mozilla Foundation Security Advisory 2026-102: CVE-2026-100779
vendor_mozilla·CVSS 8.8
CVE-2026-100779 [HIGH] Mozilla Foundation Security Advisory 2026-102: CVE-2026-100779
Mozilla Foundation Security Advisory 2026-102
CVE: CVE-2026-100779
Product: Thunderbird
Impact: moderate
Fixed in: Thunderbird 140.17
Mozilla
Mozilla Foundation Security Advisory 2026-99: CVE-2026-100779
vendor_mozilla·CVSS 8.8
CVE-2026-100779 [HIGH] Mozilla Foundation Security Advisory 2026-99: CVE-2026-100779
Mozilla Foundation Security Advisory 2026-99
CVE: CVE-2026-100779
Product: Firefox ESR
Impact: moderate
Fixed in: Firefox ESR 140.17
VulDB
Mozilla Firefox up to 115.41/140.16/153.3/156 XSLT use after free (WID-SEC-2026-3654)
vuldb·2026-10-03·CVSS 8.8
CVE-2026-100779 [HIGH] Mozilla Firefox up to 115.41/140.16/153.3/156 XSLT use after free (WID-SEC-2026-3654)
A vulnerability, which was classified as critical, has been found in Mozilla Firefox up to 115.41/140.16/153.3/156. This issue affects some unknown processing of the component XSLT. This manipulation causes use after free.
The identification of this vulnerability is CVE-2026-100779. It is possible to initiate the attack remotely. There is no exploit available.
It is advisable to upgrade the affected component.
GHSA
Use-after-free in the XSLT component.
ghsa_unreviewed·2026-09-29
CVE-2026-100779 [HIGH] CWE-416 Use-after-free in the XSLT component.
Use-after-free in the XSLT component. This vulnerability was fixed in Firefox ESR 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17.
No detection rules found.
No public exploits indexed.
https://bugzilla.mozilla.org/show_bug.cgi?id=2068417https://www.mozilla.org/security/advisories/mfsa2026-100/https://www.mozilla.org/security/advisories/mfsa2026-101/https://www.mozilla.org/security/advisories/mfsa2026-102/https://www.mozilla.org/security/advisories/mfsa2026-103/https://www.mozilla.org/security/advisories/mfsa2026-97/https://www.mozilla.org/security/advisories/mfsa2026-98/https://www.mozilla.org/security/advisories/mfsa2026-99/
2026-09-29
Published